The present invention relates in general to a variable valve operating mechanism for variably controlling lift characteristics of an intake or exhaust valve (hereinafter referred to as intake/exhaust valve) in accordance with an angular position of a control shaft and more specifically to a learning apparatus and method for a variable valve control of an internal combustion engine, particularly for learning and storing a sensor output reference value of a control shaft sensor.
Unexamined Japanese Patent Publication No. 2003-41955 discloses a variable valve operating mechanism for driving an intake/exhaust valve in timed relation with a crankshaft of an internal combustion engine while being capable of varying lift characteristics of the intake/exhaust valve in accordance with a variation of an angular position of a control shaft and a learning system therefor. The system is configured to drive, by means of an actuator, a control shaft to a minimum operation angle position that is a reference position after stoppage or at start of an engine, learn an output of a control shaft sensor and store the learned output as a sensor output reference value. Similarly, Unexamined Japanese Patent Publication No. 2002-349215 discloses a technique for driving, by means of an actuator, a control shaft to a reference position during self-shut after stoppage of an engine, learning an output of a control shaft at that time and storing the learned output as a sensor output reference value.